Granisetron base or endo-1-methyl-N-(9-methyl-9-azabicycle[3.3.1]non-3-yl)-1H-indazole-3-carboxamide has the following structure:

Granisetron acts as an antagonist of 5-HT (5-hydroxytriptamine), is useful as an antiemetic and is marketed in the form of a hydrochloride.
Granisetron was described for the first time in European patent EP 200444 where, in example 6, Granisetron base is described as an oil.
Said European patent describes how to obtain it by reaction between 1-methylindazole-3-carboxylic acid chloride and endo-3-amino-9-methyl-9-azabicycle-[3.3.1]-nonane.
Other processes for preparing it were also disclosed in patent ES2129349, in which the basic form of Granisetron is not isolated, while example 2 of international patent application WO97/30049 again describes it as an oil.
Chemical products in oil form are awkward to use and difficult to purify, since column chromatography is usually required. Moreover, pharmaceutical products in the form of oil are not suitable for pharmaceutical formulations.
Metastable polymorph forms are neither suitable since may change in an uncontrolled way.
A stable polymorph form of said compound have not yet been described and, therefore, nor their crystalline structure.
In order to overcome the disadvantages of the state of the art, the present authors have found a solid form of Granisetron base and a stable polymorphic form thereof.